Photoresistor trigger for cine camera film drive - uses shutter blade to control light striking photoresistor and balance comparator circuit preventing exposure when light level is too low

摘要

The cine camera motor is switched by the shutter blade so that film is not used when light levels are unsuitable. Light striking a photoresistor causes an imbalance in a comparator circuit controlling the shutter blade drive motor. The shutter blade is driven to control the light striking the photoresistor and balance the comparator circuit but, as a determinable light level, an abutment on the blade opens a switch to disconnect the circuit to the film transport motor. Reconnection of the film drive motor circuit follows automatically.